This invention relates to a positioning apparatus for positioning an object member at a desired position and to a machining apparatus, such as a laser beam trimming machine, for machining the object member.
Various positioning apparatus of the type are already known. For example, a positioning apparatus is disclosed in U.S. Pat. No. 4,423,959 issued to Kiwao Nakazawa et al and assigned to Nippon Kogaku K.K. The positioning apparatus includes a projecting device which is for projecting a light beam towards an object member, such as a semiconductor wafer. The object member has a mark which is provided on a part thereof. In the positioning apparatus of the example, the mark is composed of a group of short line segments which are aligned in one direction.
In order to carry out positioning operation of the object member, the light beam linearly scans the object member in another direction which is selected in compliance with a relative movement between the object member and the projecting device. In response to the light beam, the mark produces a particular beam which is called a diffracted beam in the apparatus according to the Nakazawa et al patent. The diffracted beam has a maximum intensity when the light beam intersects the mark. Responsive to the maximum intensity, it is possible to carry out the positioning operation about the object member.
However, it is incapable to quickly carry out the positioning operation of the object member in the positioning apparatus of the type. This is because scanning is carried out depending on the relative movement between the object member and the projecting device. More particularly, judgement can not be made until completion of the scanning by the relative movement about whether or not the diffracted beam has the maximum intensity.
Such a positioning apparatus can be included in a machining apparatus, such as a laser beam trimming machine. In that case, it is a matter of course that the machining apparatus is incapable of quickly machining a predetermined position of the object.